Beware of Respawn!
If you tackle the Molten Core with enough experience, speed, and gear, the instance can be cleared in no time, and you can go home before the defeated trash enemies respawn.
However, Sauercrowd does not have the gear or the experience to approach such speed. On the contrary, the raid is scheduled for at least 4 hours on Sunday, and it may even extend into the evening.
If the streamer guild makes full use of this time window, they will inevitably have to deal with respawns in between. This can become dangerous, for example, if they need to bring in replacement players or if they have to backtrack through half the instance to reach the final boss Ragnaros.